Spinning UV light writer

[David] has always wanted use UV LEDs to write on a phosphorescent surface ever since saw an article about it on Make. He accidentally purchased UV LEDs when he meant to buy purple ones, so he figured that his mistake was all the reason he needed to give UV light writing a try.

He built a PIC16F628 UV POV board using the LEDs, and while manually swiping the writer across various glow in the dark surfaces was cool, he wanted to keep the POV board stationary, moving the writing medium instead. He bought some phosphorescent vinyl, but found that it wasn’t too flexible, meaning he could not use a conveyor belt approach for his display. One day it dawned on him that a vinyl ring might work pretty well, and using a motor from an old cassette player, he constructed the UV writer you see above.

It seems to work pretty well despite a small flaw in the UV ring, and while [David] is happy with the results, he already has plenty of ideas in mind for the second revision.

I used a turntable. I’m still using the original turntable motor and circuitry to drive it, so it’s not the best. It would be much better if I could control it with the micro. I’d swap out the motor, but it’s a direct drive, and the motor is part of the circuit board. It looks to be a brushless motor, possibly sensored, but I don’t know how to control one of those, and haven’t bothered to improve it yet.

Don’t forget that we can trade parameters for effect manipulation. Crank up the UV intensity or use more sensitive/longer afterglow materials.One approach might be like a ship’s wiper port- Rotating glass, fixed wiper. With a spinning transparent glow material for a HUD effect?

Old CRTs couldn’t be used, they don’t glow nearly long enough, and it takes a ridiculous amount of power to make it even glow of a little bit and have and pov effect at all. I have a 80-100 mW UVish laser (405nm ±10) and swiping it across the screen gives barely any afterglow, and definitely not enough for a POV display.

old flouros and CFLs have almost no effect, so those wouldn’t work either.

Glow parts from toys are long lasting glow, and would work well.

Glow bits on tires are probably reflectors, and wouldn’t work at all (no persistence).

You could use glow paint and paint a piece of glass to do what you’re describing (or make the wiper move and the glass stationary).

Perhaps using some fiber to guide the UV light to a more tight spacing might work? That way you can up the resolution.
I assume the cheap stuff guides UV when I say that.
Problem then becomes to get enough light to make the surface glow, so you’d need some sort of fiber that was wide in one direction and thin in the other, or make a setup where several fibers for a row to each LED and the column is one fiber thick.
Like so (fibers are represented by the dot):
…. all guided to LED#1
…. all guided to LED#2
…. all guided to LED#3
etc.

if the rotation direction is the long dimension of the fiber bundle, there’s no reason to use multiple fibers. Just direct more light into a single fiber and leave the LED on for a longer period of time.

Well the exit diameter of a fiber is very small, and it’s hard to push all the light of a led into it, it would require a lens or several lenses I imagine.
You’d have to experiment to know what works and what’s needed though.

Gah! I’m so slow at publishing. Also, why no love hackaday? I made a display like this (http://thouton.wordpress.com/ghost-display/) about a year ago but couldn’t get any coverage of my blog. I’m about to release the code for my implementation if anybody is interested – It’ll be open source (waves carrot). Also I’ve tried to make it as configurable as possible (while keeping it simple) and as hackable as possible (simple interfaces and code) and super extensible.

I like this type of display, but I saw something done with UV lasers that blew me away (can’t find it now, but it was on Hackaday a while back).

One idea that I had for further awsome is a cylinder like braclet that rotated around your wrist – a watch. Sure it would be hard to make, but possibly do-able. Anywho, if anybody is interested in my code let me know and I’ll submit something to HaD when I’ve got the source up (should be the next couple of days).